The present invention relates generally to a method and system for providing improved tracking for musical instrument noise reduction systems and more particularly concerns such tracking in high gain guitar noise reduction systems. Noise reduction has continued to evolve and improve for many years providing the musician ongoing improvements in sound quality and reduced noise in live performances. Numerous patents have been issued for improvements in the area of noise reduction technology, including many of my inventions covered under U.S. Pat. Nos. 4,647,876, 4,696,044, 4,881,047, 4,893,099, 5,124,657, 5,263,091, 5,404,498 and 5,493,617. One benefit of my recently issued U.S. Pat. No. 6,944,305 is tracking the envelope of the input signal to provide a variable release response based on tracking the decay of the input signal.
While these improvements have offered a major advance in the overall performance of noise reduction for musicians, and in particular the guitarist, there has been a lack of improvement available in reducing the noise, particularly in extremely high gain applications. When the noise reduction system has the ability to track the level and wide dynamic range of the instrument directly, it's easy to have a controlled, and accurate response from the noise reduction system. However, typical modern guitarists use extremely high gain and distortion as a major part of their sound palate. When driving any guitar preamplifier into extreme distortion, the output signal becomes highly compressed and the dynamic range is reduced to as little as 5 to 10 decibels. This reduction in dynamic range makes it extremely difficult, if not impossible, for a noise reduction system to determine the difference between the background noise and the desirable instrument signal. The most common place to inset a noise gate or noise reduction system is in the effects loop of the instrument amplifier, which allows the noise reduction system to improve the dynamic range of the post distort signal. While this will reduce the background noise of the system, it also requires switching the noise reduction out of the signal path when the musician changes from a high gain distortion setting to a clean un-distorted sound. If the noise reduction system is not switched out, the threshold of the noise reduction system will be set so high that low-level signals will be undesirably truncated or attenuated. The improvements of the '305 patent finally allow the guitarist to eliminate the common problem of squealing feedback between short staccato notes caused by using extremely high gain in the guitar preamplifier if the noise reduction system is used between the guitar and the input of the amplifier. Noise reduction systems based on the '305 patent, if connected between the instrument and the preamplifier, will allow extremely quick response reducing the gain of the instrument before feedback occurs by tracking the wide dynamic range of the guitar. However, when the noise reduction system is inserted between the instrument and the input of the preamplifier, there is no effect of reducing the noise at the output of the high gain preamplifier. Using two channels of noise reduction will improve this problem but, as described above, requires the noise reduction system at the output of the preamplifier to operate with as little as 5 to 10 decibels of dynamic range and also requires the system to be switched out to avoid the side effect of chopping off any low level signal in a low gain setting.
It is, therefore, an object of this invention to provide a noise reduction system which does not track the small dynamic range at the output of a high gain guitar preamplifier. It is also an object of the invention to provide an improved multi-channel noise reduction system in which the level detection circuit for all channels tracks the instrument directly and allows one noise reduction channel to be placed between the instrument and the input of the guitar preamplifier and a second noise reduction channel to be inserted in the effects loop of the typical guitar amplifier. Another object of the current invention is to allow the guitar amplifier to be switched from a high gain setting to a low gain or clean setting without any need to change the threshold setting of the noise reduction system. Yet another object of the invention is to provide a system where both low-level downward expansion and dynamic low pass filtering as a composite noise reduction audio processing block for multiple channels can track the instrument directly. Yet another object of the current invention is to provide the ability to have multiple audio channels of noise reduction for use in a stereo or multi-channel guitar system where all of the audio channels detection circuit track the instrument directly and the audio signal can be inserted after the use of a high gain preamplifier.